1. Field of the Invention
The present invention relates generally to access networks, such as wireless local area networks (WLANs) and, more specifically, to a mechanism for requesting and admitting an emergency Voice over Internet Protocol phone call through an access network in which Extensible Authentication Protocol (EAP) is used.
2. Description of the Related Art
Telephone (voice) calls can be placed not only through the public telephone network and wireless (e.g., cellular) telephone networks but also through data networks such as the Internet. The most common technology for transmitting voice calls through data networks is known as Voice over Internet Protocol (VoIP). A person can place a VoIP call using an computer equipped with a microphone and speaker and suitable software, or using a desktop VoIP telephone, handheld VoIP telephone, or any other user terminal that can encode and transmit voice in accordance with IP and associated protocols.
In some respects, VoIP lags behind the more well-established telephone technologies. For example, while there are well-established mechanisms for ensuring that calls placed to emergency operators through the public telephone network (e.g., by dialing “911” in the United States and similar numbers in other countries) are properly handled, mechanisms for doing so through data networks are still under development. Some of the issues that need to be addressed in developing such mechanisms include how the call is admitted through an access network and how to handle authentication of the user.
A wireless local area network (WLAN) is a type of access network in which data is transmitted by radio communication between the user's terminal and a nearby device known as an access point. The access point, in turn, is part of the access network, and the user can transparently access computers or other devices connected to the access network from the user's terminal, as though the user's terminal were connected to the network via a wired connection. For example, a user having a wireless VoIP terminal can place a telephone call through the access network in a manner very similar to that in which one can place a telephone call using a cellular telephone.
A WLAN standard developed by the Third-Generation Partnership Program (3GPP), a consortium of telecommunications standards bodies operating under a collaboration agreement, provides an architecture in which a user's terminal can connect via a WLAN to a remote data network, such as the Internet or a core network of cellular telecommunication systems. The mechanism as it applies to cellular telecommunication operators inter-working with WLANs is defined in 3GPP's Release 6 documents, TS 23.234 and TS 24.234.
“Public WLAN” is a term that refers to the placement of access points in publicly accessible areas, such as airport lounges, waiting rooms, and coffeehouses, giving rise to areas known as “hotspots” in which users can access remote networks to check e-mail, surf the Internet, upload and download files, and so forth. Accordingly, a user having a suitable wireless VoIP terminal in a hotspot can place a VoIP telephone call. However, not all WLANs (or access networks supporting IP transport) are able to handle emergency VoIP calls. This lack of support for VoIP emergency calls in many public WLANs is due to two main reasons. Firstly, not all public WLANs are capable of routing emergency calls (with appropriate information such as location) to emergency call centers. Secondly, WLANS are not able to recognize and thereby admit users making emergency calls without appropriate credentials.
Generally, when a user initially attempts to use an access network to gain access to remote networks, one or more “authentication, authorization and accounting” (AAA) processes occur to ensure that the user is authorized to use the network and that the user can be billed accordingly (generally, through the user's home network, such as one that provides the user with data and voice (e.g., cellular, VoIP, etc.) telecommunications services). The user's home network includes an AAA server that performs AAA functions in conjunction with an AAA proxy server that is part of the access network. The authentication process involves routing AAA information to the user's home network's AAA server. Because all public WLAN operators may not have roaming agreements directly with the operator of the user's home network, routing in such cases must occur via one or more intermediary networks or brokers, whose operators have roaming agreements with the WLAN operator, the user's home network operator, or other intermediary network operators.
The Internet Engineering Task Force (IETF), an open consortium of network designers, operators, vendors, and researchers concerned with the evolution of the Internet architecture and the smooth operation of the Internet, has defined a protocol known as Extensible Authentication Protocol (EAP) that provides an authentication framework supporting multiple authentication methods. EAP can be used by various access network technologies, including WLAN technology.
One difficulty in the authentication process is selecting the intermediary network(s) through which to route the AAA information. In the most common authentication schemes, the user's terminal plays a primary role in the selection of intermediary networks. 3GPP has suggested the use of EAP to have the WLAN provide or “advertise” information or “hints” to the user's terminal to aid the terminal in selecting one or more intermediary network(s) through which to route the AAA information. The information can be, for example, a list of the WLAN operator's roaming partners, i.e., intermediary operators with whom the WLAN operator has a roaming agreement. 3GPP's suggestion includes that the terminal indicate the selected routing by inserting information into or “decorating” a Network Access Identifier (NAI) and transmitting it to the WLAN.
There may also be potential intermediary networks that do not have the capability of properly routing emergency calls in the manner in which such calls are required to be routed in the public switched telephone network (PSTN) and certain other networks. For example, when a person dials “911” on an ordinary landline telephone, the switching office not only connects the caller to an emergency call center but also obtains the caller's location and transmits that information to the call center as well. Therefore, when a caller is initiating an emergency call via an access network such as a WLAN, it would be desirable to route such location information along with the call to the local emergency call center and to otherwise handle the emergency call in a manner analogous to that in which such calls are handled in the PSTN, even in cases in which the caller cannot be authenticated in the conventional manner. Accordingly, it can be seen that a need remains in the art for a system and method for admitting and routing an emergency phone call through an access network. It is to such a system and method that the present invention is primarily directed.